This invention relates to a diesel particulate filtering device trapping a particulate matter (PM) in exhaust gas of an internal combustion engine such as a diesel engine.
More particularly, this invention relates to a technology detecting clogging of this diesel particulate filtering device to incinerate the trapped PM and to recovery the filtering device.
The Harmful PM (particulate matter) is contained in exhaust gas emitted from the diesel engine in car use. It has been attempted that an exhaust pipe is provided with the diesel particulate filtering device constituted by a diesel particulate filter unit having a filter formed nonwoven fabric or the like made of a ceramics textile in order to clean these PM.
This diesel particulate filtering device is constituted by providing a singular or a plurality of diesel particulate filter units.
In the diesel particulate filtering device provided with the singular diesel particulate filter unit, PM in the exhaust gas is trapped by the diesel particulate filter unit. And then, when the filter of the diesel particulate filter unit is clogged up with this trapped PM, the diesel particulate filter unit is recovered.
Moreover, in the diesel particulate filtering device provided with a plurality of diesel particulate filter units, one diesel particulate filter unit traps PM in the exhaust gas to switch the exhaust gas passage when the filter of this diesel particulate filter unit is clogged up with this trapped PM. Moreover, the clogged diesel particulate filter unit is treated to recovered, while PM is trapped in succession by the other diesel particulate filter unit.
In this treatment for recovery, PM trapped by the filter is burnt and treated by a heating source such as an electric heater provided on the diesel particulate filter unit and to solve clogging.
In prior art, determination of a timing for recovery of the diesel particulate filter unit has been performed by comparing a difference in pressure or a ratio of pressure between the front and the back of the diesel particulate filter unit with a predetermined determination value, thereby to be designed to control such that the treatment for recovery is performed, when this difference in pressure or ratio of pressure exceeds the predetermined-determination value. This difference in pressure or ratio of pressure is obtained by measuring an exhaust pressure by exhaust pressure sensors provided on the front and the back of the diesel particulate filter unit.
The determination value for determination should be changed in response to a running condition of the engine, since the exhaust pressure is changed in accordance with changes in a speed of revolution and a read of the engine or the like when defining this difference in pressure as a criterion of determination. Therefore, control becomes complicated.
Moreover, the ratio of pressure at clogging becomes approximately constant, since the ratio of pressure is changed in response to the running condition of the engine in a small amount when defining the ratio of pressure as a criterion of determination. Therefore, the determination value for determination should not be changed in response to a running condition of the engine. As a result, control becomes relatively simple.
However, it is frequent the case where it is installed on commercial vehicles such as a truck in the case of a diesel engine which the diesel particulate filtering device is required. This commercial vehicle has been diversified in the exhaust characteristic, since an exhaust pipe with a different shape is provided depending upon the purpose of using a vehicle.
Therefore, the determination value determining for an initiating timing of the treatment for recovery should be adjusted every each vehicle, since the exhaust pressure of the outlet side of the diesel particulate filtering device is changed in response to the shape of the exhaust pipe even though providing the diesel particulate filtering device with the same size.
Furthermore, there also are variations to some degree in characteristics in the pressure sensor detecting the exhaust pressure. Output of the pressure sensor is changed due to time aging, in particular. Therefore, the determination value should be re-adjusted. However, there have been problems that determination of the presence or absence of necessity of re-adjustment of the determination value and re-adjustment of the determination take time, since the degree of this time aging is different depending upon each motor vehicle.
Still more, an initial adjustment of this determination value is performed by replacing the predetermined determination value stored in advance in a diesel particulate filter controller (controller) with the determination value determined renewedly by calculating to a shape of these exhaust pipes in the prior art. Accordingly, there have been the problems that rewrite operation becomes complicated and a rewrite operator should have expert knowledge on programming.
This invention is devised for solving the prior problems mentioned above, and the object of the invention is to provide a diesel particulate filtering device in which the determination value for determining the recovery time can be corrected simply by determination-value update means without changing contents of the control program when mounting the diesel particulate filtering device on the motor vehicle and coping with variations in output of the pressure sensor due to time aging and so forth.
The diesel particulate filtering device provided with the singular diesel particulate filter unit for accomplishing the object described above is constituted as follows.
A diesel particulate filtering device which is provided with the diesel particulate filter unit for cleaning the exhaust gas of an internal combustion engine, and in which cleaning of the exhaust gas by the diesel particulate filter unit and recovery of the diesel particulate filter unit clogged up with this cleaning of the exhaust gas are performed, wherein an exhaust pressure sensor provided on a downstream side of the diesel particulate filter unit and a diesel particulate filter controller for inputting a detected value of the exhaust pressure sensor to determine a recovery time of the diesel particulate filter unit are provided, as well as determination-value update means in which the diesel particulate filter controller compares the detected value of the exhaust pressure sensor with a predetermined-standard exhaust pressure value set and stored in advance to reset a determination value for determining the recovery time is provided.
Moreover, a diesel particulate filtering device provided with a plurality of diesel particulate filter units for accomplishing the object described above is constituted as follows.
A diesel particulate filtering device which is provided with a plurality of diesel particulate filter units for cleaning the exhaust gas of an internal combustion engine, and in which cleaning of the exhaust gas by the diesel particulate filter unit and recovery of the diesel particulate filter unit clogged up with this cleaning of the exhaust gas are performed alternately while switching an inflow passage of the exhaust gas to the diesel particulate filter unit, wherein exhaust pressure sensors provided on an upstream side and a downstream side of the diesel particulate filter unit respectively and a diesel particulate filter controller for inputting detected values of the exhaust pressure sensors to determine a recovery time of the diesel particulate filter unit and to control so as to switch the inflow passage of the exhaust gas to the diesel particulate filter unit are provided, as well as determination-value update means in which the diesel particulate filter controller compares the detected value of the exhaust pressure sensor with a predetermined-standard exhaust pressure value set and stored in advance to reset a determination value for determining the recovery time is provided.
According to this constitution, the predetermined determination value stored in advance in the diesel particulate filter controller can be reset simply based on a measured value of an actual exhaust pressure. It has become unnecessary to calculate the determination value for update to the shape of the exhaust pipe different every each vehicle renewedly and to rewrite contents in memory for the determination value. Therefore, installing operation of the diesel particulate filter unit controller can be simplified. Still more, the expert knowledge on programming becomes unnecessary to the operator, since determination-value update means automatically initiates update operation when being started.
Moreover, since the determination value is updated in accordance with the measured value of the actual exhaust pressure, it can be obtained more correctly than the case to obtain by calculating from the shape of the exhaust pipe, whereby the determination value can be set more reasonably.
Moreover, in the diesel particulate filtering device, the determination values for determining the recovery time are defined as the determination values relating to a ratio between the exhaust pressure value of the upstream side and the exhaust pressure values of the downstream side of said diesel particulate filter units, and the determination values to be reset are defined as a value obtained by multiplying the standard determination value by the predetermined-standard exhaust pressure value of the downstream side, as well as dividing it by the measured exhaust pressure values of the downstream side.
Namely, the determination value to be reset is defined by a formula;
Determination Value to be Reset=(Standard Determination Value)xc3x97(Standard Exhaust Pressure Value of Downstream Side)/(Actually-Measured Exhaust Pressure Value of Downstream Side). 
A fluctuation from the standard value is corrected and can be stored as a new determination value by providing with this determination-value update means. Therefore, the pressure ratio for determining in the case where the diesel particulate filter is clogged is set simply.
Moreover, the ratio between the upstream-side exhaust pressure value and the downstream-side exhaust pressure value of the diesel particulate filter unit is hard to be affected by the speed of revolution and the read of the engine, and becomes approximately constant value to the clogged condition, whereby the recovery time can be determined simply by using this pressure ratio for determination of the recovery time.
In the diesel particulate filtering device, the determination-value update means are started through an external signal.
According to this constitution, the update has come to be able to perform simply by inputting this external signal from an external switch or the like. Moreover, the diesel particulate filtering device can be provided with a correcting function for reduction in output of the exhaust pressure sensor due to time aging.
Moreover, the more reasonable determination value can be set simply by inputting this signal, even in the case where output of the exhaust pressure sensor is changed due to time aging except for the case where mounting on the vehicle.
The recovery time can be determined appropriately according to the diesel particulate filtering device of these constitution, whereby the vehicle on which this diesel particulate filtering device is mounted can be improved in quality.